Biology past paper questions

Name two more pieces of apparatus they would need to make sure this is a controlled investigation. (2)

• Thermometer

• Timer

• Measuring cylinder

Outline the method that the students would use to carry out an investigation into the effect of temperature on the diffusion on rate in their model cells. (6)

• Add glucose solution to the dialysis tubing

• Secure tubing after adding glucose

• Place tubing in water bath and remove sample at set time intervals

• Add Benedict’s to sample to test for glucose

• Use colorimeter to obtain absorption values

• Use calibration curve to estimate the concentration of glucose

• Repeat at different temperatures

Explain these results in terms of the effect of temperature on the rate of diffusion. (3)

• As the temperature increases the kinetic energy of the glucose molecules increases

• Glucose molecules diffuses at a faster rate

• Greater rate between 10 and 20 degrees C

Based only on the data in the table, suggest a hypothesis on the formation of aneurysm. (1)

Higher collagen : elastin ration leads to a larger aneurysm

Explain the roles of valves in veins (2)

• They prevent backflow of blood as it is at low pressure

• Allows one way flow back to heart

The smooth muscle content in the arteriole walls is more than double the smooth muscle content in the walls of the arteries

Explain how arterioles are better adapted than arteries to allow the blood to flow into an individual organ (3)

• Relaxation of the smooth muscle causes vasodialation

• Regulates blood flow to capillaries

• Pressure of blood is higher in artery

• As blood flows from the artery to the arteriole, pressure falls

• So capillary will not rupture

Details of hormonal and nervous control are not required (6)

• SAN starts the wave of excitation

• Electrical activity causes atria to contract

• Non conducting tissue

• Pace maker

• Myogenic

• AVN picks up electrical activity from SAN

• AVN causes a slight delay

• Delay ensures atria have stopped contracting before ventricles contract

• Ventricles only contract when wave of excitation in Purkyne fibres

• Makes sure blood has left the atria otherwise less blood will exit the heart

• AVN stimulates Bundle of His in septum

• Bundle of His conducts wave of excitation to apex of heart

• Purkyne fibres in walls of ventricles

• Ensure ventricles contract at same time

Explain why a large multicellular plant needs a transport system but a small multicellular plant does not. (2)

In the larger plant the SA:V ration is smaller so the diffusion pathway is longer

State the change that needs to be made to this test to enable protein to be detected (1)

Add Biuret instead of sodium hydroxide

Describe the chemical test you would carry out to see if the srudents’ findings were correct. Include the apparatus and reagents you would use and the results you would expect. (6)

Lipids apparatus

• Test tube

• Filter paper and funnel

• Pipette

Emulsion test and reagents

• Add test solution to ethanol

• mix with water

• can filter and add water to filtrate

• Clear to cloudy

Starch apparatus

• Test tube

• Pipette

Iodine test and reagents

• Add a few drops of iodine

• Orange to blue-black

The students were then asked to carry out an experiment to determine the glucose conc of another test using a colorimeter

Describe how the students would use a colorimeter in their experiment. (3)

• Calibrate colorimeter with distilled water

• Add red filter to colorimeter

• Place samples in a curvette

• Use a range of known glucose concentrations

• Measure absorbance of glucose solutions

State the properties of collagen that make it suitable for it in ligaments (2)

• Fibrous

• Insoluble

• Tensile strength

• Resistant to stretching

Suggest and explain how stem cells might be used to help treat parkinson’s disease (2)

Stem cells can differentiate into nerve cells

Would allow normal body movements

Describe the role of mitosis in fragmentation. (1)

Produces many genetically identical cells

Suggest two further improvements they could have made and give reason for the improvements you have suggested. (4)

• Same mass of pieces

• For same surface area

• Pieces from the same betroot

• to control pigment conc

Explain the results between 20 and 70 using your knowledge of the structure and properties of phospholipid molecules in the plasma membrane. (6)

• Membrane least permeable at 20

• At 30/40/50 pigment escapes from gaps between moving phospholipids

• As temp increases kinetic energy increases

• More phospholipid movement

• Membrane more permeable

• More pigment loss so higher absorbance figure

• 60/70, membrane distrupted

• Bilayer breaks down

• Membrane very permeable

• Large increase in pigment loss

• Laege increase in absorbance figure

Include structure and properties of phospholipids

The size of the cell increases during G2 in the cell cycle

State one other process that takes place during G2 (1)

• Protein synthesis

• DNA checked for errors

• DNA repair

Describe the importance of differential staining for observing cells undergoing mitosis (1)

Makes chromosomes visible

Name the type of bond broken by the enzyme lactase and describe what happens when the bond is broken (2)

Hydrolysis, water is added

Compare prophase in mitosis with prophase in meiosis

Similarities

• Chromosomes condense

• nuclear envelope breaks down

• Spindle fibres form

Differences

• Meiosis has two prophases

• Homologous chromosomes pair in prophase 1

• Crossing over occurs

A common symptom of lactose intolerance in adults is the creation of extra fluid in the large intestine suggest why. (2)

Lactose lowers the water potential

Causing water to move inside the cells by osmosis

Identify three errors made in the students description and write the correction for each error (3)

• starts at the SAN not AVN

• at B the AV valve doesnt open, it closes

• at C the semi lunar valve doesnt open, it closes

Explain how haemoglobin acts as a buffer (2)

CO2 and water form carbonic acid

Carbonic acid dissociates giving H+

H+ binds to Hb

So CO2 can be carries as HCO3-

Describe how the apparatus can be used to model the changes that take part during inspiration in mammals (6)

• Pull down the elastic sheet- models the diaphragm flattening

• Volume in ball jar increases- models the thorax volume increasing

• Pressure in bell jar gets lower- models thorax pressure decrease

• Air pressure outside now higher than in bell jar- models higher pressure outside lungs

• Air pushed into balloons- models air inflating lungs

Balloons → models two lungs

Elastic sheet → represents diaphragms

Glass tubing → trachea

cannot model contraction of external intercostal muscles

State two differences between the closed circulatory system of sea bass and the closed circulatory system of a mammal (2)

Sea bass blood goes through the heart once vs mammal twice

Sea bass single vs mammal double

Describe how the structure of each type of blood vessel is adapted to its function (6)

Artery

• Carry blood away from the heart at high pressure

• Thick elastic layer / elastin enables them to withstand pressure and alllows them to stretch and recoil

• Collagen provides support, maintains shape and volume

• Smooth muscle contracts and relaxes to change the size of the lumen

Veins

• Carry blood back to the heart

• no pulse so needs to move against gravity

• Thinner elastic layer, no stretch / recoil

• Have valves to prevent backflow of blood

• More collagen than arteries to give structural support as they carry large volumes of blood

Capillaries

• Allow substances to be exchanges

• Walls once cell thick

• RBC travel in single file

Sjogren’s syndrome is a rare condition that can reduce the production of mucus

Suggest how the upper respiratory tract of a person with Sjorgen’s syndrome might be affected. (1)

More coughing

Describe what is meant by the term esterification (2)

• Condensation reaction

  • Joins carboxylic acid and alcohol

Outline how respiratory systems in a bony fish and in an insect are adapted to maximise ventilation and gaseous exchange. (6)

Bony fish ventilation

• Watter enters moth

• Volume and pressure changed in buccal cavity

• Water flows over gills

• water leaves via operculum

Bony fish gas exchange

• Large SA

• thin

• short diffusion distance

• counter current system

Insect ventilation

• Muscular movement

• abdominal pumping

Two components in mammalian gas exchange include cartilage and elastic fibres. (2)

• Cartilage stopes trachea from collapsing

• Elastic fibres allow alveoli to recoil